The impression I get is that it's the same motivation as men who flash. It's about using sexual aggression to deliberately shock. Flashers tend to target the young and the old, in order to increase shock and upset. And this person is choosing to do this in a school, to young adolescents. I don't think that's a coincidence.
It seems fairly obvious that the same standards of professional dress should be required of Transwomen as are required of women. I can't imagine a female teacher being supported in wearing Z size breast prosthetics or sexualised clothing. What are the school leadership thinking?? Why on earth does all ability to think and apply good judgement disappear as soon as it relates to anyone Trans.